The present invention relates to a conveyor apparatus for continuously conveying workpieces at a constant pitch, and more particularly to conveyor equipment suitable for carrying out a plurality of working processes in a production facility. Specifically, the present invention relates to a conveyor suitable for carrying out characteristic measurement, selection, taping, and other processes on a small workpiece such as an electronic component conveyed by means of an automatic mechanism.
Conventionally when producing a taped type electronic component whose wire type lead terminals are held on a base tape formed with notches beforehand, an electronic component element is attached to the lead terminals to complete the electronic component on the base tape as disclosed in U.S. Pat. No. 4,954,207. Electronic components produced as described above are subjected to characteristic measurement and selection processes while being conveyed, held on the base tape, and further to a taping process. The above-mentioned method has the advantage that the electronic component is stably held on the base tape while being conveyed; however, since the electronic component cannot be removed directly upward from base tape, the taping operation is difficult and the base tape cannot be used again after the taping operation is completed.
After completing an electronic component having plate type lead terminals by attaching an electronic component element to lead terminals (lead frame) formed from a hoop material, the electronic component is separated from others and transferred to a conveyor. A base tape, as described above, cannot be used. In order to convey an electronic component with plate type lead terminals, a conveying method is used in which workpiece holders with recess portions opening upward are attached at a constant pitch to an endless chain, driven intermittently, and electronic components are put in each of these recess portions.
However, since the electronic component is merely put in, the recess portion of a workpiece holder, it can be displaced or fall off the workpiece holder due to an inertial force at the time of intermittent feed. Furthermore, when the electronic component is conveyed vertically or in a circular arc direction, the electronic component cannot be prevented from being displaced or falling off the workpiece holder. For the above reasons, the workpiece conveyance direction is limited to almost horizontal directions; this allows little latitude with regard to the workpiece conveyance direction.
Conventionally when a plurality of processes having different processing times are included in a production facility, the processing speed of the entire production facility is generally adjusted to the process requiring the longest time. Therefore, another process requiring a short processing time cannot start its operation until the process requiring the longest processing time is completed; this results in slow processing speed and low efficiency of the entire production facility. Particularly when processing times of processes differ extremely, the above-mentioned problem becomes much more acute.
Furthermore, in view of the recent growing trend of multi-sort small-quantity production, when a component requiring a different processing time is transferred to the production facility line, or when the processing time of the process requiring the longest processing time is changed, the processing time of the entire production facility must be changed; this results in requiring a significant amount of time for adjustment procedures.